linux-kernel - Re: [PATCH v2 1/6] Documentation: fpga: dfl: Add documentation for DFHv1

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Message-ID: <b0689af0-511-dd5d-8e3-cca69d609cb0@linux.intel.com>
Date:   Fri, 23 Sep 2022 17:40:40 +0300 (EEST)
From:   Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>
To:     Matthew Gerlach <matthew.gerlach@...ux.intel.com>
cc:     hao.wu@...el.com, yilun.xu@...el.com, russell.h.weight@...el.com,
        basheer.ahmed.muddebihal@...el.com, trix@...hat.com,
        mdf@...nel.org, linux-fpga@...r.kernel.org,
        linux-doc@...r.kernel.org, LKML <linux-kernel@...r.kernel.org>,
        tianfei.zhang@...el.com, corbet@....net,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-serial <linux-serial@...r.kernel.org>,
        Jiri Slaby <jirislaby@...nel.org>, geert+renesas@...der.be,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        niklas.soderlund+renesas@...natech.se, phil.edworthy@...esas.com,
        macro@...am.me.uk, johan@...nel.org, Lukas Wunner <lukas@...ner.de>
Subject: Re: [PATCH v2 1/6] Documentation: fpga: dfl: Add documentation for
 DFHv1

On Fri, 23 Sep 2022, Ilpo Järvinen wrote:

> On Fri, 23 Sep 2022, matthew.gerlach@...ux.intel.com wrote:
> 
> > From: Matthew Gerlach <matthew.gerlach@...ux.intel.com>
> > 
> > Add documentation describing the extensions provided by Version
> > 1 of the Device Feature Header (DFHv1).
> > 
> > Signed-off-by: Matthew Gerlach <matthew.gerlach@...ux.intel.com>
> > ---
> > v2: s/GUILD/GUID/
> >     add picture
> > ---
> >  Documentation/fpga/dfl.rst | 49 ++++++++++++++++++++++++++++++++++++++
> >  1 file changed, 49 insertions(+)
> > 
> > diff --git a/Documentation/fpga/dfl.rst b/Documentation/fpga/dfl.rst
> > index 15b670926084..7c786b75b498 100644
> > --- a/Documentation/fpga/dfl.rst
> > +++ b/Documentation/fpga/dfl.rst
> > @@ -561,6 +561,55 @@ new DFL feature via UIO direct access, its feature id should be added to the
> >  driver's id_table.
> >  
> >  
> > +Extending the Device Feature Header - DFHv1
> > +===========================================
> > +The current 8 bytes of the Device Feature Header, hereafter referred to as
> > +to DFHv0, provide very little opportunity for the hardware to describe itself
> > +to software. Version 1 of the Device Feature Header (DFHv1) is being introduced
> > +to provide increased flexibility and extensibility to hardware designs using
> > +Device Feature Lists.  The list below describes some of the goals behind the
> > +changes in DFHv1:
> > +
> > +* Provide a standardized mechanism for features to describe
> > +  parameters/capabilities to software.
> > +* Standardize the use of a GUID for all DFHv1 types.
> > +* Decouple the location of the DFH from the register space of the feature itself.
> > +
> > +Modeled after PCI Capabilities, DFHv1 Parameters provide a mechanism to associate
> > +a list of parameter values to a particular feature.
> > +
> > +With DFHv0, not all features types contained a GUID.  DFHv1 makes the GUID standard
> > +across all types.
> > +
> > +With DFHv0, the register map of a given feature is located immediately following
> > +the DFHv0 in the memory space.  With DFHv1, the location of the feature register
> > +map can be specified as an offset to the DFHv1 or as an absolute address.  The DFHv1
> > +structure is shown below:
> > +
> > +    +-----------------------------------------------------------------------+
> > +    |63 Type 60|59 DFH VER 52|51 Rsvd 41|40 EOL|39 Next 16|15 VER 12|11 ID 0|
> > +    +-----------------------------------------------------------------------+
> > +    |63                                 GUID_L                             0|
> > +    +-----------------------------------------------------------------------+
> > +    |63                                 GUID_H                             0|
> > +    +-----------------------------------------------------------------------+
> > +    |63                 Address/Offset                            1|  Rel  0|
> > +    +-----------------------------------------------------------------------+
> 
> Is something missing here given the layout is claimed (in 2/6) to be:
> 
> "DFHv1 Register Offset definitons
> In DHFv1, DFH + GUID + CSR_START + CSR_SIZE_GROUP + PARAM_HDR + PARAM_DATA"
> 
> ?

Ah, I think I've figured it out, PARAM_HDR + PARAM_DATA combo is repeated 
n times (rather than the params being covered by the "PARAM_DATA")?

-- 
 i.

> > +    |63 Size of register set  32|Params 31|30 Group    16|15 Instance      0|
> > +    +-----------------------------------------------------------------------+
> > +    |63 Next parameter offset 32|31 Param Version 16|15 Param ID           0|
> > +    +-----------------------------------------------------------------------+
> > +    |63                 Parameter Data                                     0|
> > +    +-----------------------------------------------------------------------+
> > +
> > +                                  ...
> > +
> > +    +-----------------------------------------------------------------------+
> > +    |63 Next parameter offset 32|31 Param Version 16|15 Param ID           0|
> > +    +-----------------------------------------------------------------------+
> > +    |63                 Parameter Data                                     0|
> > +    +-----------------------------------------------------------------------+
> > +
> >  Open discussion
> >  ===============
> >  FME driver exports one ioctl (DFL_FPGA_FME_PORT_PR) for partial reconfiguration
> > 
> 
>